Radium Engineering Air Oil Separator (AOS-R) Kit, Subaru 02-14/2015+ STi/Saab 9-2X 02-07 WRX STi and 04-08 Forester XT

02-07 WRX, 04-08 FXT, 08-14 STI, 08-14 WRX, 15 STI, 18 STI, Radium Engineering

Pricing: $449.95

Free ground shipping on all order over $100.00 (some exclusions may apply)


High-powered modified Subaru engines tend to generate excessive blow-by oil and gasses. In these cases, an ordinary small catch can mayquickly fill with oiland not be adequate. Like the Radium EngineeringSubaru Dual Catch Can Kit, the AOS (Air Oil Separator) kit is responsible for keeping blow-by oil and other pollutants out of the intake pipe, manifold, turbocharger, and intercooler during all engine loads. The main difference is thatan AOS system returns what is collected back into the oil pan so there is no servicing required.The built-in heater keeps water from condensing in the AOS.And because water is more dense than oil, there is an integrated water trap found around the bottom perimeter of the can. This prevents water from descending into the oil pan if ever present. Furthermore, because the water is trapped against the heater, it will eventually boil and evaporate out of the system.

CLICK HERE for a more in-depth look at the Subaru AOS

The AOS is constructed of three CNC machined sections that screw together and are sealed with O-rings.


AOS Height: 6.94" (top of dipstick to bottom of AOS)
AOS Diameter: 3.45" Round
AOS Capacity: 20.3 oz (600mL)

-Effectively raises the octane and increases engine performance with cleaner inlet air
-Prevents oil buildup in the intake or intercooler system walls, throttle body, intake manifold, etc.

-Lowers hydrocarbon emissions

What is included?
-Machined alumium Radium Engineering Air Oil Separator
-Specially designed mounting bracket (see note at bottom of page)
-All necessary SAE J30R7 rated PCV/Emissions hose
-Coolant hoses and fittings
-All necessary aluminum fittings and hose-ends
-Stainless steel mounting hardware

20-0207-02 Mounting Compatibility
02-07 Impreza WRX
02-07 Impreza WRX STi
04-08 Forester XT
05-06 Saab 9-2X Aero

20-0207-08 Mounting Compatibility
08-14 Impreza WRX
08-14 Impreza WRX STi
2015+ Subaru STi

The primary difference between the two kits is thespecialized mounting bracket that secures to OEM holes on the RH strut tower, as detailed below:

*For 02-05 Subarus with a cable-actuated throttle body, ourCruise Control Relocation Bracketmust be used.
*For RHD vehicles, ourUniversal AOSmust be used for custom mounting and plumbing.

*The Radium AOS kit may not be compatible with all other aftermarket products. Please inspect pictures carefully before purchasing.

Product Series



Shipping Information

  • Item Requires Shipping
  • 5.0 lbs.
  • Free ground shipping on all order over $100.00 (some exclusions may apply)

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